Upgrade to 1.1 -> index.php error

I had no trouble with the previous upgrade, so perhaps was a bit confident with this one! I followed the directions for 1.1, but seem to have broken the themes, getting the following error on any public page (the back-end still works):

Catchable fatal error: Argument 1 passed to Zend_Controller_Front::registerPlugin() must be an instance of Zend_Controller_Plugin_Abstract, instance of Omeka_Core given, called in /home/.backyards/(USERNAME)/(WEBSITENAME)/omeka/index.php on line 22 and defined in /home/.backyards/(USERNAME)/(WEBSITENAME)/omeka/application/libraries/Zend/Controller/Front.php on line 719

The caps/brackets are my edits.

Any ideas? What do I need to fix?

Hi pcoutas,

What plugins do you have on your Omeka installation? And, did you modify any of your themes to use a plugin function that may be deactivated? That may be the culprit.

Also, try switching themes to see if that helps. If that works, it may be a problem with a specific theme.